Energizing circuit for magnetron using parallel transformers

ABSTRACT

A magnetron energizing circuit uses two transformers of the high leakage reactance type having isolated secondaries with an end terminal of each secondary connected to a common point. The secondaries are connected to series condensers respectively to provide leading current flowing in the secondary circuits at all times to produce saturation in the respective cores of the transformers under the secondaries whereby to achieve substantially constant current and good regulation for variations in the primary voltage. The combined secondaries and condensers are connected through a rectifier or rectifiers to a magnetron used for heating purposes, the magnetron participating in the overall operation of the circuit and being of the continuous wave type so as to achieve heating as for example in cooking ovens.

United States Patent 11 1 Feinberg 1451 Aug. 26, 1975 1 1 ENERGIZINGCIRCUIT FOR MAGNETRON USING PARALLEL TRANSFORMERS Albert E. Feinberg,Chicago, 111.

[73] Assignee: Advance Transformer Company,

Chicago, Ill.

[22] Filed: Sept. 24, 1973 [21] Appl. No.: 400,352

[75] Inventor:

[52] US. Cl. 315/105; 315/277; 315/282;

321/15; 321/24; 321/27; 323/61; 328/267 [51] Int. Cl. l-l02j 3/24 [58]Field of Search 315/94, 101, 105, 200 R,

[56] References Cited UNITED STATES PATENTS 3,584,288 6/1971 Bochm328/262 X Primary Examiner-Paul L. Genslcr Armrncy, Agenl, orFirmSilverman 8L Cass, Ltd.

] 57 ABSTRACT A magnetron energizing circuit uses two transformers ofthe high leakage reactance type having isolated secondaries with an endterminal of each secondary connected to a common point. The secondariesare connected to series condensers respectively to provide leadingcurrent flowing in the secondary circuits at all times to producesaturation in the respective cores of the transformers under thesecondaries whereby to achieve substantially constant current and goodregulation for variations in the primary voltage. The combinedsecondaries and condensers are connected through a rectifier orrectifiers to a magnetron used for heating purposes, the magnetronparticipating in the overall operation of the circuit and being of thecontinuous wave type so as to achieve heating as for example in cookingovens.

11 Claims, 3 Drawing Figures A.C. LINE ENERGIZING CIRCUIT FOR MAGNETRONUSING PARALLEL TRANSFORMERS BACKGROUND OF THE INVENTION The inventionherein relates to magnetron energizing circuits for providing pulsed dcpower to a magnetron from a relatively low frequency low voltage ac.power source.

The principles of operation of the circuits herein are based upon thedisclosures of US. Pat. No. 3,396,342 and reference may be had to saidpatent for the details thereof. Suffice it to say that the power supplycircuit which includes the magnetron is a highly simplified oneutilizing a transformer having a primary winding connected to an ac.source and a secondary winding in step-up relationship therewith butphysically isolated therefrom and loosely coupled so as to provide ahigh leakage reactance during the operation of the transformer. A seriescondenser provides a continuous leading current in the secondary circuitand hence its capacitive reactance is chosen to be greater than thetotal effective inductive reactance in series therewith, the latterinductive reactance comprising the leakage reactance and the inductivereactance introduced by the secondary winding itself. The componentsdescribed are connected through rectifier means to a continuous wavemagnetron, the rectifier means being either a single rectifier elementacting in conjunction with the condenser to provide a half-wave voltagedoubler type of circuit; or a pair of rectifier elements connected withtwo condensers effectively to produce a fullwave voltage doubler type ofarrangement. Another modification uses a full-wave rectifier in astraight rectified pulsed voltage circuit. In all cases the magnetronanode is grounded and the cathode is at high potential, the cathodebeing energized either by an independent transformer or by means of afilament winding closely coupled to the primary.

All three circuits are in commercial use as of the present time,primarily in domestic heating ovens using magnetrons of relatively lowpower.

It is possible to use similar magnetrons which do not have higher anodevoltages but which are nevertheless capable of achieving approximatelytwice the power output. In order to do so using the basic circuit, itwould be necessary to design transformers which are capable of handlinglarger currents and/or higher voltages. This would be expensive. Theinvention herein teaches circuits which utilize the same transformersthat are utilized in low power circuits but with unique parallelconnections to achieve generally the same power. In each of thecircuits, the only components which are doubled in quantity are thetransformers and the condensers.

SUMMARY OF THE INVENTION The invention comprises a circuit in whichthere are two transformers, capacitive means, and a rectifier allconnected to provide the pulsed dc. to a magnetron with good regulation.The primaries of the transformers are connected to an ac line ofrelatively low frequency and low voltage in parallel. The secondariesare physically isolated from the respective primaries and coupled in amanner to provide a high leakage reactance in the secondaries during theoperation thereof. One terminal of each secondary is connected to acommon point with the same instantaneous polarity and the other terminalof each secondary is connected through respective first and secondcapacitive reactance means such as, for example, a series condenser, therespective capacitor reactance means having such capacitance as toprovide a leading current in the respective secondary winding during theoperation of the circuit. Both capacitive reactance means are connectedto a continuous wave magnetron whose anode is grounded and whose cathodeis at high potential, there being rectifier means between the magnetronand the capacitive reactance means so that a rectification takes place.In this way the alternating current produced by the combination of thecapacitive reactance means and the secondary of the transformer isrectified to pulsed do which energizes the magnetron. The connections ofcapacitive reactance and rectifying means are such that there is eitherstraight rectification, half-wave voltage doubling, or full-wave voltagedoubling. Three different circuits for providing this type ofperformance are disclosed.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a circuit diagram of amagnetron energizing apparatus constructed in accordance with theinvention in the configuration of a half-wave voltage doubler circuit;

FIG. 2 is a circuit diagram of a magnetron energizing apparatusconstructed in accordance with the invention in the configuration of afull-wave voltage doubler circuit; and

FIG. 3 is a circuit diagram of a magnetron energizing apparatusconstructed in accordance with the invention in the configuration of afull-wave rectifier circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. I, thecircuit is designated generally by the reference numeral 10 andcomprises basi cally two transformers T1 and T2, capacitive reactancemeans in the form of two condensers C1 and C2, a rectifier which in thiscase comprises a single diode D1, a magnetron of the continuous wavetype which is designated M, and a filament transformer T3 for themagnetron filament.

The transformers TI and T2 include respectively primary windings P1 andP2 each of which is connected in parallel across the line represented bythe terminals 12 and 14. This line could be, for example, volts 60 Hertzas provided by ordinary mains. Each transformer has an iron core oflaminated electrical steel or other ferromagnetic design which issymbolized by the parallel lines at 16 and 18 respectively and eachtransformer has an isolated secondary winding designated respectively S1and S2. The relationship between the turns of the respective windings ofthe transformers is such that a substantially high voltage will bedeveloped in the secondary windings, usually of the order of kilovoltsfor a commercial magnetron. The secondaries, S1 and S2, are looselycoupled with respect to the primaries P1 and P2 and there may be shuntsarranged in the core as indicated at 20 and 22 so that it is understoodthat during the operation of the transformers TI and T2 a high leakagereactance will be developed in the secondary windings. One terminal ofeach secondary winding is connected at a common point 24 which, in thiscase, is grounded. The opposite terminals of the secondary windings areconnected to the condensers CI and C2 respectively, these condensersthereby comprising series connected capacitive reactance means. Theblack dots shown at the terminals of the secondaries opposite point 24signify that the instantaneous voltage polarity for the parallelconnected secondaries S1 and S2 is the same so that the secondaries areintended to be energized and function simultaneously. The condensers Cland C2 have a common terminal at 26 which connects to the lead line 28that is maintained at high voltage. The rectifier D1 is connected fromthe line 28 to ground. The line 28 is also connected to the cathode 30of the magnetron M, the anode 32 of the magnetron being connected toground by way of the lead 34.

The pick-up probe 36 feeds the waveguide 38 with high frequency energyproduced by the magnetron M and the wave guide leads to a horn 40 whichis located in a magnetron oven (not shown). The circuit 10 of FIG. 1 isthe most simplified of the circuits since it utilizes only one condenserin addition to the added transformer. The operation of the circuit is nodifferent than that of the circuit shown in FIG. of said US. Pat. No.3,396,342, except that the power is substantially doubled for the samecircuit parameters.

The transformer T3 is connected to the line by means of the leads 42 and44 and is illustrated as a completely separate transformer. Its primaryP3 and secondary S3 are closely coupled as in the case of ordinary powertransformers, the secondary winding being connected across the filament46.

Transformers of the construction of T1 and T2 as disclosed in said US.Pat. No. 3,396,342, may have filament windings wound directly onto theprimary windings in which case those filament windings will be connectedin parallel and directly to the filament 46 instead of utilizing anadditional transformer T3, or may be supplied on one of the twotransformers TI and T2.

One additional advantage of the circuit of FIG. I is that the secondarywindings S1 and S2 may be grounded as shown at 24 thereby decreasing theneed for high voltage insulation as the case would be in other circuitswhich will be described hereafter.

As mentioned, the circuit 10 functions as a half-wave voltage doublertype of circuit. The diode D1 in this case serves as a return path forcurrent through the capacitive reactance means CI and C2 on alternatehalf cycles of the voltage output.

The apparatus 10' illustrated in FIG. 2 differs from the apparatus 10 ofFIG. I in that it is a full wave voltage doubler configuration of thecircuit. The rectifying means in this case comprise the two diodes D1and D2 which operate on alternate half cycles in conjunction with thecapacitive reactance means. Thus, on one half cycle the capacitivereactance means C1 and C3 operate in conjunction with the diode D2 andon the other half cycle the capacitive reactance means C2 and C4 act inconjunction with the diode D1 during discharge thru the magnetron.

Again, the transformers T1 and T2 have their prima ries P1 and P2 inparallel connected to the line 12, I4 and their secondaries S1 and S2connected much the same as the case in FIG. I. The common terminal inthis circuit is 241 but it cannot be grounded because of the particulartype of configuration and hence the insulation requirements of thetransformers T1 and T2 are somewhat more stringent than in the case ofthe configuration of FIG. 1. By simple analysis it can readily be shownthat the circuit of FIG. 2 is in effect two halfwave voltage doublercircuits back to back but utilizing only the two transformers T1 and T2as taught by FIG. 1

FIG. 3 illustrates a third apparatus 10 which is a full wave rectifierconfiguration of the circuit of the invention. The circuit is amodification of that illustrated in FIG. 2 of said US. Pat. No.3,396,342. Again, the transformers T1 and T2 have their primaries P1 andP2 connected in parallel across the ac line 12, 14. The secondarywindings SI and S2 are high leakage reactance secondary windings with acommon terminal at 24 that in this case is also not grounded and theiropposite terminals connected through series condtnsers Cl and C2 to therectifier means which in this case comprise a bridge rectifier formed ofthe diodes D1, D2, D3, and D4. The line 28 in this circuit is connectedto the terminal 50 of the bridge rectifier S2 and the opposite terminal54 of the rectifier is connected through the line 56 to the terminal 24.The left-hand terminal 53 of the rectifier 52 is grounded and theright-hand terminal 60 of the rectifier is connected through the line 62to the cathode 30 of the magnetron M. The remaining details of thecircuit 10" are obvious and the operation is not materially differentfrom the operation of the apparatus shown in FIG. 2 of said US. Pat. No.3,396,342.

The transformers T1 and T2 in every case may be no different from thosewhich are available commercially for lower power circuits and an exampleis described in detail in said US. Pat. No. 3,396,342.

It is most convenient to tie the transformer secondaries S1 and S2together at the common point 24, but the circuits lltl and 10" will notbe affected in any Way if the condenser and secondary winding in eachseries combination is interchanged. Thus, for example, in FIG. 1, Cl andS1 could be interchanged without effect.

The use of two condensers in circuits l0 and 10" instead of a singlecommon condenser provides stability. Even if transformers TI and T2 weremade on the identical production line, it is practically impossible tohave identical characteristics in the secondaries. One secondary windingwill start to develop a slightly higher voltage and will commence toupset the balance, resulting in a wasteful circulating current in theloop including the secondaries. The condensers inside the loop developvoltages which offset this tendency. It is feasible to use an economicalcondenser having a common foil and independent individual foils insteadof two physically separate condensers.

What it is claimed and desired to secure by Letters Patent of the UnitedStates is:

I. An operating circuit for energizing a magnetron from an ac. line ofrelatively low voltage and low frequency which comprises a. a magnetronhaving an anode and a cathode;

b. a generally constant current transformer and condenser meanscombination which comprises i. two step-up transformers each having aprimary winding connected to said ac. line;

ii. each transformer having a secondary winding isolated from itsprimary winding but coupled in high leakage reactance operating relationto its respective primary winding, the secondary windings each having afirst terminal at the same instantaneous polarity connected to a commonjuncture; and

iii. paired condenser means with one terminal of each pair connected inseries with one of the respective secondary windings, and with a commonmidpoint,

c. the anode and cathode of the magnetron being connected to thecombination to be subjected to the output voltage thereof; and

d. rectifier means connected to the common midpoint of said pairedcapacitor means providing inphase return paths for current through thecondenser means on alternate half-cycles of the voltage output, saidcurrent from each secondary winding being additive in total pulsemagnitude the ca pacitive reactance of the condenser means being sizedwith respect to the inductive reactance in said transformer andcondenser means combination so as to provide a leading current in thesecondary circuit including both secondary windings to provide goodregulation notwithstanding normal variations of the line voltage.

2. An operating circuit as claimed in claim 1 in which said commonjuncture and magnetron anode are at ground potential, the rectifiermeans comprise a rectifier having its cathode connected to ground andits anode connected to the cathode of the magnetron, and said condensermeans comprising two condensers, each being connected in series with arespective one of said secondary windings to form individualsecondary-series-condenser combinations, said last-mentionedcombinations being connected from said first common juncture to theanode of the rectifier and forming therewith said common midpoint, theresulting configuration acting as a half-wave voltage doubler circuitduring operation.

3. An operating circuit as claimed in claim 1 in which said rectifiermeans comprise two rectifiers with the cathode of the first rectifierand the anode of the second rectifier connected to said common juncture,the anode of the first rectifier being connected. to the cathode of themagnetron and the cathode of the second rectifier being connected to theanode of the magnetron, the condenser means comprising two pairs ofcondensers, each pair being connected across the magnetron and thesecond terminal of each secondary winding being respectively connectedto the junctions between the respective pairs of condensers, theresulting configuration acting as a full-wave voltage doubler circuitduring operation.

4. An operating circuit as claimed in claim 1 in which the rectifiermeans comprise a four terminal bridge rectifier having its positiveterminal connected to the magnetron anode and its negative terminalconnected to the magnetron cathode, the common juncture being connectedto the third terminal of the bridge rectifier, each secondary windinghas a respective condenser of said condenser means connected in seriestherewith whereby to form individual secondaryscries-condensercombinations, the combinations being connected between said commonjuncture and the fourth terminal of said bridge rectifier.

5. An operating circuit as claimed in claim I in which each secondarywinding has a respective condenser of said condenser means individuallyconnected in a series arrangement for one half cycle operation and eachsecondary and series condenser combination is connected to said commonmidpoint.

6. The operating circuit as claimed in claim 5 in which the firstterminals of the secondaries are connected together to form the commonjuncture, the second terminals of the secondaries are respectivelyconnected to one terminal of said respective condensers and the secondterminals of said condensers are connected together to form the commonmidpoint.

7. An operating circuit as claimed in claim 5 in which each secondarywinding has an additional respective condenser of said condenser meansindividually connected in a series arrangement for the alternate halfcycle operation.

8. In a magnetron energizing circuit for providing pulsed do. to saidmagnetron and comprising a high leakage reactance, substantiallyconstant current output, iron-core, power transformer and condensermeans combination, the transformer having a primary winding adapted tobe energized from a low voltage ac. line and a secondary winding involtage step-up relationship, the magnetron having anode and cathodeconnected respectively to the terminals of the secondary winding withthe condenser means comprising a portion of series loop circuitryincluding the magnetron and secondary winding, and rectifier meansconnected across the magnetron providing a return path through thecondenser means at least on alternate half cycles of current, thesecondary winding and condenser means forming a first seriescombination; means for increasing the power output of the energizingcircuit without materially altering any of the components thereof andcomprising:

a second transformer substantially the same as said first-mentionedtransformer and having a secondary winding equivalent to thefirst-mentioned secondary winding, second condenser means connected withthe second-mentioned secondary winding to form therewith a second seriescombination, the combinations being connected in parallel with thesecondaries polarized to have common instantaneous voltage polarityduring operation to operate in concert, and the primary winding of thesecond transformer being adapted to be connected for energizing from aline in parallel with the firstmentioned primary winding, and thecondenser means in each case having a capacitance of such value relativeto the total inductance of the secondary winding with which it iscombined during operation such as to produce at that time a leadingcurrent in each secondary winding and the circuit has a half-wavevoltage doubler configuration, with the rectifier means comprising arectifier having its anode connected to the magnetron cathode, itscathode connected to the magnetron anode, and both combinationsconnected across the rectifier.

9. The invention as claimed in claim 8 in which both secondary windingsare arranged at one end of their respective combinations and connectedtogether at that end, said end being grounded and the magnetron anodebeing grounded.

10. In a magnetron energizing circuit for providing pulsed dc to saidmagnetron and comprising a high leakage reactanee, substantiallyconstant current output, iron-core, power transformer and condensermeans combination, the transformer having a primary winding adapted tobe energized from a low voltage a.c.

line and a secondary winding in voltage step-up relationship, themagnetron having anode and cathode connected respectively to theterminals of the secondary winding with the condenser means comprising aportion of series loop circuitry including the magnetron and secondarywinding, and rectifier means connected across the magnetron providing areturn path through the condenser means at least on alternate halfcycles of current, the secondary winding and condenser means forming afirst series combination; means for increasing the power output of theenergizing circuit without materially altering any of the componentsthereof and comprising:

a second transformer substantially the same as said first-mentionedtransformer and having a secondary winding equivalent to thefirst-mentioned secondary winding, second condenser means connected withthe second-mentioned secondary winding to form therewith a second seriescombination, the combinations being connected in parallel with thesecondaries polarized to have common instantaneous voltage polarityduring operation to operate in concert, and the primary winding of thesecond transformer being adapted to be connected for energizing from aline in parallel with the firstmentioned primary winding and thecondenser means in each case having a capacitance of such value relativeto the total inductance of the secondary winding with which it iscombined during operation such as to produce at that time a leadingcurrent in each secondary winding and the circuit has a full-wavevoltage doubler configuration, with the rectifier means comprising apair of series connected rectifiers having a common juncture and theanode of one connected to the magnetron cathode while the cathode of theother is connected to the magnetron anode, the series combinations eachhaving a pair of condensers arranged in series with its secondarywinding connected respectively between condensers at their one terminalsand to the common juncture at their second terminals, the condenserpairs being connected across the two rectifiers, the operation of thecircuit being such that each secondary is in series with alternatecondensers of its pair on alternate half cycles.

11. In a magnetron energizing circuit for providing pulsed dc. to saidmagnetron and comprising a high leakage reactance, substantiallyconstant current output, iron-core, power transformer and condensermeans combination, the transformer having a primary winding adapted tobe energized from a low voltage a.c. line and a secondary winding involtage step-up relationship, the magnetron having anode and cathodeconnected respectively to the terminals of the secondary winding withthe condenser means comprising a portion of series loop circuitryincluding the magnetron and secondary winding, and rectifier meansconnected across the magnetron providing a return path through thecondenser means at least on alternate half cycles of current, thesecondary winding and condenser means forming a first seriescombination; means for increasing the power output of the energizingcircuit without materially altering any of the components thereof andcomprising:

a second transformer substantially the same as said first-mentionedtransformer and having a secondary winding equivalent to thefirst-mentioned secondary winding, second condenser means connected withthe second-mentioned secondary winding to form therewith a second seriescombination, the combinations being connected in parallel with thesecondaries polarized to have common instantaneous voltage polarityduring operation to operate in concert, and the primary winding of thesecond transformer being adapted to be connected for energizing from aline in parallel with the firstmentioned primary winding and thecondenser means in each case having a capacitance of such value relativeto the total inductance of the secondary winding with which it iscombined during operation such as to produce at that time a leadingcurrent in each secondary winding and the circuit has a full-waverectifier configuration, with the rectifier means comprising a bridgerectifier having one pair of opposite terminals connected across themagnetron and the other pair connected across the both combinations.

1. An operating circuit for energizing a magnetron from an a.c. line ofrelatively low voltage and low frequency which comprises a. a magnetronhaving an anode and a cathode; b. a generally constant currenttransformer and condenser means combination which comprises i. twostep-up transformers each having a primary winding connected to saida.c. line; ii. each transformer having a secondary winding isolated fromits primary winding but coupled in high leakage reactance operatingrelation to its respective primary winding, the secondary windings eachhaving a first terminal at the same instantaneous polarity connected toa common juncture; and iii. paired condenser means with one terminal ofeach pair connected in series with one of the respective secondarywindings, and with a common midpoint, c. the anode and cathode of themagnetron being connected to the combination to be subjected to theoutput voltage thereof; and d. rectifier means connected to the commonmidpoint of said paired capacitor means providing in-phase return pathsfor current through the condenser means on alternate half-cycles of thevoltage output, said current from each secondary winding being additivein total pulse magnitude the capacitive reactance of the condenser meansbeing sized with respect to the inductive reactance in said transformerand condenser means combination so as to provide a leading current inthe secondary circuit including both secondary windings to provide goodregulation notwithstanding normal variations of the line voltage.
 2. Anoperating circuit as claimed in claim 1 in which said common junctureand magnetron anode are at ground potential, the rectifier meanscomprise a rectifier havIng its cathode connected to ground and itsanode connected to the cathode of the magnetron, and said condensermeans comprising two condensers, each being connected in series with arespective one of said secondary windings to form individualsecondary-series-condenser combinations, said last-mentionedcombinations being connected from said first common juncture to theanode of the rectifier and forming therewith said common midpoint, theresulting configuration acting as a half-wave voltage doubler circuitduring operation.
 3. An operating circuit as claimed in claim 1 in whichsaid rectifier means comprise two rectifiers with the cathode of thefirst rectifier and the anode of the second rectifier connected to saidcommon juncture, the anode of the first rectifier being connected to thecathode of the magnetron and the cathode of the second rectifier beingconnected to the anode of the magnetron, the condenser means comprisingtwo pairs of condensers, each pair being connected across the magnetronand the second terminal of each secondary winding being respectivelyconnected to the junctions between the respective pairs of condensers,the resulting configuration acting as a full-wave voltage doublercircuit during operation.
 4. An operating circuit as claimed in claim 1in which the rectifier means comprise a four terminal bridge rectifierhaving its positive terminal connected to the magnetron anode and itsnegative terminal connected to the magnetron cathode, the commonjuncture being connected to the third terminal of the bridge rectifier,each secondary winding has a respective condenser of said condensermeans connected in series therewith whereby to form individualsecondary-series-condenser combinations, the combinations beingconnected between said common juncture and the fourth terminal of saidbridge rectifier.
 5. An operating circuit as claimed in claim 1 in whicheach secondary winding has a respective condenser of said condensermeans individually connected in a series arrangement for one half cycleoperation and each secondary and series condenser combination isconnected to said common midpoint.
 6. The operating circuit as claimedin claim 5 in which the first terminals of the secondaries are connectedtogether to form the common juncture, the second terminals of thesecondaries are respectively connected to one terminal of saidrespective condensers and the second terminals of said condensers areconnected together to form the common midpoint.
 7. An operating circuitas claimed in claim 5 in which each secondary winding has an additionalrespective condenser of said condenser means individually connected in aseries arrangement for the alternate half cycle operation.
 8. In amagnetron energizing circuit for providing pulsed d.c. to said magnetronand comprising a high leakage reactance, substantially constant currentoutput, iron-core, power transformer and condenser means combination,the transformer having a primary winding adapted to be energized from alow voltage a.c. line and a secondary winding in voltage step-uprelationship, the magnetron having anode and cathode connectedrespectively to the terminals of the secondary winding with thecondenser means comprising a portion of series loop circuitry includingthe magnetron and secondary winding, and rectifier means connectedacross the magnetron providing a return path through the condenser meansat least on alternate half cycles of current, the secondary winding andcondenser means forming a first series combination; means for increasingthe power output of the energizing circuit without materially alteringany of the components thereof and comprising: a second transformersubstantially the same as said first-mentioned transformer and having asecondary winding equivalent to the first-mentioned secondary winding,second condenser means connected with the second-mentioned secondarywinding to form therewith a second series combination, the combinationsbeinG connected in parallel with the secondaries polarized to havecommon instantaneous voltage polarity during operation to operate inconcert, and the primary winding of the second transformer being adaptedto be connected for energizing from a line in parallel with thefirst-mentioned primary winding, and the condenser means in each casehaving a capacitance of such value relative to the total inductance ofthe secondary winding with which it is combined during operation such asto produce at that time a leading current in each secondary winding andthe circuit has a half-wave voltage doubler configuration, with therectifier means comprising a rectifier having its anode connected to themagnetron cathode, its cathode connected to the magnetron anode, andboth combinations connected across the rectifier.
 9. The invention asclaimed in claim 8 in which both secondary windings are arranged at oneend of their respective combinations and connected together at that end,said end being grounded and the magnetron anode being grounded.
 10. In amagnetron energizing circuit for providing pulsed d.c. to said magnetronand comprising a high leakage reactance, substantially constant currentoutput, iron-core, power transformer and condenser means combination,the transformer having a primary winding adapted to be energized from alow voltage a.c. line and a secondary winding in voltage step-uprelationship, the magnetron having anode and cathode connectedrespectively to the terminals of the secondary winding with thecondenser means comprising a portion of series loop circuitry includingthe magnetron and secondary winding, and rectifier means connectedacross the magnetron providing a return path through the condenser meansat least on alternate half cycles of current, the secondary winding andcondenser means forming a first series combination; means for increasingthe power output of the energizing circuit without materially alteringany of the components thereof and comprising: a second transformersubstantially the same as said first-mentioned transformer and having asecondary winding equivalent to the first-mentioned secondary winding,second condenser means connected with the second-mentioned secondarywinding to form therewith a second series combination, the combinationsbeing connected in parallel with the secondaries polarized to havecommon instantaneous voltage polarity during operation to operate inconcert, and the primary winding of the second transformer being adaptedto be connected for energizing from a line in parallel with thefirst-mentioned primary winding and the condenser means in each casehaving a capacitance of such value relative to the total inductance ofthe secondary winding with which it is combined during operation such asto produce at that time a leading current in each secondary winding andthe circuit has a full-wave voltage doubler configuration, with therectifier means comprising a pair of series connected rectifiers havinga common juncture and the anode of one connected to the magnetroncathode while the cathode of the other is connected to the magnetronanode, the series combinations each having a pair of condensers arrangedin series with its secondary winding connected respectively betweencondensers at their one terminals and to the common juncture at theirsecond terminals, the condenser pairs being connected across the tworectifiers, the operation of the circuit being such that each secondaryis in series with alternate condensers of its pair on alternate halfcycles.
 11. In a magnetron energizing circuit for providing pulsed d.c.to said magnetron and comprising a high leakage reactance, substantiallyconstant current output, iron-core, power transformer and condensermeans combination, the transformer having a primary winding adapted tobe energized from a low voltage a.c. line and a secondary winding involtage step-up relationship, the magnetron having anode and cathodeconnected respectively tO the terminals of the secondary winding withthe condenser means comprising a portion of series loop circuitryincluding the magnetron and secondary winding, and rectifier meansconnected across the magnetron providing a return path through thecondenser means at least on alternate half cycles of current, thesecondary winding and condenser means forming a first seriescombination; means for increasing the power output of the energizingcircuit without materially altering any of the components thereof andcomprising: a second transformer substantially the same as saidfirst-mentioned transformer and having a secondary winding equivalent tothe first-mentioned secondary winding, second condenser means connectedwith the second-mentioned secondary winding to form therewith a secondseries combination, the combinations being connected in parallel withthe secondaries polarized to have common instantaneous voltage polarityduring operation to operate in concert, and the primary winding of thesecond transformer being adapted to be connected for energizing from aline in parallel with the first-mentioned primary winding and thecondenser means in each case having a capacitance of such value relativeto the total inductance of the secondary winding with which it iscombined during operation such as to produce at that time a leadingcurrent in each secondary winding and the circuit has a full-waverectifier configuration, with the rectifier means comprising a bridgerectifier having one pair of opposite terminals connected across themagnetron and the other pair connected across the both combinations.